Semiconductor devices are used in a variety of electronic applications, such as personal computers, cell phones, digital cameras, and other electronic equipment, as examples. Semiconductor devices are typically fabricated by sequentially depositing insulating or dielectric layers, conductive layers, and semiconductive layers of material over a semiconductor substrate, and patterning the various layers using lithography to form circuit components and elements thereon.
A transistor is an element that is utilized extensively in semiconductor devices. There may be millions of transistors on a single integrated circuit (IC), for example. A common type of transistor used in semiconductor device fabrication is a metal oxide semiconductor field effect transistor (MOSFET). A transistor typically includes a gate dielectric disposed over a channel region, and a gate formed over the gate dielectric. A source region and a drain region are formed on either side of the channel region within a substrate or workpiece.
In complementary metal oxide semiconductor (CMOS) devices, both positive and negative channel devices are used in complementary configurations. The positive and negative channel devices of CMOS devices are typically referred to as p channel metal oxide semiconductor (PMOS) and n channel metal oxide semiconductor (NMOS) transistors. A PMOS transistor is formed in an n well (e.g., a well implanted with n type dopants) and an NMOS transistor is formed in a p well. A shallow trench isolation (STI) region is typically formed between the n well and p well of the PMOS transistor and the NMOS transistor, respectively.
In some transistor designs, it is desirable to introduce stress to the channel region to improve the transistor performance.
What are needed in the art are improved methods and structures for introducing stress in transistors and other semiconductor devices.